Domain investor here. Some, but not all of the advice here is absolutely dreadful and is an example of why you should not take advice from random strangers on the internet. Some basic rules if you wish to keep the domain: * Don't offer to sell the domain. If you are contacted by a prospective buyer, just decline, saying that the domain is not for sale. Don't counter-offer or enter into discussions or negotiations. *…
If your name is Apple and you somehow obtain new domain named apple.newtld you have a chance to loose the domain if there is any way it can be seen as profiting off of the association with the APL. For example if you put ads on a page that is nominally your personal page it can be seen as getting traffic from people who mistakenly came to this page since there is very little chance they came legitimately.
If it is large company they will be looking at every possible way to get your domain and the only way to fight it is to either spend huge amount of money on lawyers or not give any pretext, however small.
You are also as likely to lose the domain by a targeted attack by people who hope to then sell the domain. If you have a nice domain name you need to invest a bit of thought in protecting it from takover (locking the domain, protecting your information, not using your regular phone number, phone, email, laptop, etc. to have anything to do with the admin access to the domain).